Preheat the oven to 350°F and lightly grease a 13x9-inch baking dish. Slice the acorn squash in half lengthwise and remove the seeds. Arrange the halves cut-side down in the baking dish, cover, and bake for 40-45 minutes, or until the squash is fork-tender.
While the squash is baking, prepare the rice. In a large saucepan, combine the rice, water, and soy sauce, bringing the mixture to a boil. Reduce the heat to low, cover, and let it simmer for 15-18 minutes, or until the liquid is fully absorbed and the rice is tender.
In a separate skillet, melt the butter over medium heat and sauté the chopped onion until softened. Add the diced apples and continue to sauté for another 3 minutes, stirring occasionally. Remove the skillet from heat and mix in the cooked rice, shredded mozzarella, chopped walnuts, half-and-half, balsamic vinegar, honey, minced ginger, and curry powder. Stir until well combined, allowing the flavors to blend.
Turn the baked squash halves over and generously fill each cavity with the prepared rice mixture. Return the baking dish to the oven, uncovered, and bake for an additional 20-25 minutes, until the stuffing is heated through and slightly golden on top. Serve warm.